1. Field of the Invention
The present invention relates to a digital color image forming apparatus having a light emitting element array as a recording means.
2. Related Background Art
In conventional color copying machines having such a recording means and latent image forming means (for example, an yellow developing device, a magenta developing device, a cyan developing device, a black developing device, a photosensitive member and the like), recording heads and latent image forming means are spaced apart from each other side by side on an upper surface of a belt-shaped transfer medium, a recording sheet fed from a sheet supply portion is conveyed by the transfer medium, and toner images formed on the photosensitive member are successively transferred onto the recording sheet, to thereby form a color image. As shown in FIGS. 6A to 6C, in the recording head, LED (light emitting element) array chips and their drive IC ships are mounted on a single substrate, and the LED array chips and the corresponding drive IC chips are interconnected by wire bonding. Heat generated by the LED array chips and the drive IC chips is radiated through radiate plates shown in FIG. 6C. The recording head comprises the LED array chips, the drive IC chips and a connector. The LED array chip includes light emitting portions arranged in a line, and each light emitting portion has a wiring pad for connecting to the drive IC chip. The drive IC chip also has wiring pads corresponding to the respective light emitting portions. By controlling emission of light, the light emitting portions can be controlled. The LED array chip and the drive IC chip are generally interconnected by wire bonding.
However, in the above-mentioned conventional technique, the recording head is expanded entirely or partially due to thermal expansion caused by heat generated from the LED array chips and/or the drive IC chips, so that the magnification in a main scan direction is changed or color deviation occurs. Further, light emitting amounts of the LED array chips are fluctuated to thereby cause temperature fluctuation and/or density unevenness which result in poor image. Particularly, if images having local high density area(s) are continuously formed, local temperature increase will occur, to thereby cause color deviation and/or density unevenness.
Further, for example, if a full-color image is formed immediately after black images were continuously formed, since temperature of only the black recording head of the image forming means was increased, significant color deviation will occur because of difference in expansion between the recording heads.
In the conventional techniques, in order to minimize the influence of the temperature difference, the substrate is formed from expensive material having low coefficient of thermal expansion or large radiate plates are used, to resultantly make the entire apparatus expensive and bulky.
The present invention intends to eliminate the above-mentioned conventional drawbacks, and has an object to provide an image forming apparatus in which an image can be formed without color deviation.
Another object of the present invention is to provide an image forming apparatus comprising a photosensitive member, an exposure means for exposing the photosensitive member with light corresponding to image information and having a plurality of light emitting elements arranged along a direction perpendicular to a conveying direction of a recording material, a transfer means for transferring an image formed on the photosensitive member onto the recording material, and a light emission controlling means for causing the plurality of light emitting elements to emit light other than a period during which the plurality of light emitting elements emit the light in response to the image information.
A further object of the present invention is to provide an image forming apparatus comprising a photosensitive member, an exposure means for exposing the photosensitive member with light corresponding to image information and having a plurality of light emitting elements arranged along a direction perpendicular to a conveying direction of a recording material, a transfer means for transferring an image formed on the photosensitive member onto the recording material, and a light emission controlling means for controlling light emission of the light emitting elements in a non-image forming period, in accordance with light emitting times of the light emitting elements emitting the light in response to the image information.
A still further object of the present invention is to provide an image forming apparatus comprising a photosensitive member, an exposure means for exposing the photosensitive member with light corresponding to image information and having a plurality of light emitting elements arranged along a direction perpendicular to a conveying direction of a recording material, a transfer means for transferring an image formed on the photosensitive member onto the recording material. When the light emitting elements corresponding to the image information emit the light, the other light emitting elements not relating to the image information also emit the light slightly.
The other objects of the present invention will be apparent from the following detailed explanation referring to the accompanying drawings.